It is known that purine nucleic acid-related substances, such as adenosine, adenosine phosphate, and salts thereof, exhibit a moisturizing effect when applied to the skin by increasing the number of free amino acids in the horny cell layer, and, in addition, function to stimulate turnover thereby preventing drying and aging of the skin and improving the condition of rough skin. In order to obtain this effect, the application of purine nucleic acid-related substances to external preparations, such as a cosmetic, pharmaceutical or quasi-pharmaceutical preparations has been examined. It is known that purine nucleic acid-related substances have a cell proliferation promoting effect (Life Sciences, Vol. 64, No. 18, pp. 1661-1674, 1999), and it is assumed that the cell-proliferation promoting effect relates to the above-described various effects.
However, since these purine nucleic acid-related substances have high hydrophilicity, percutaneous absorption is difficult to carry out.
In order to overcome such drawbacks, for a long time a method has been sought that can more effectively exert the cell-proliferation promoting effect of purine nucleic acid-related substances when applied to the skin, etc.